Northwest Pacific cyclone 2021-02-05 0229Z

Cyclolysis is a process in which a cyclonic circulation weakens and deteriorates. Cyclolysis is the opposite of

cyclogenesis Cyclogenesis is the development or strengthening of cyclonic circulation in the atmosphere (a low-pressure area). Cyclogenesis is an umbrella term for at least three different processes, all of which result in the development of some sort of cyc ...

Extratropical cyclones

Extratropical cyclones Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are low-pressure areas which, along with the anticyclones of high-pressure areas, drive the weather over much of the Earth. Extratropical cyclones are capable of p ...

usually undergo cyclolysis after an

occluded front In meteorology, an occluded front is a type of weather front formed during cyclogenesis. The classical and usual view of an occluded front is that it initiates when a cold front overtakes a warm front near a cyclone, such that the warm air is separ ...

forms, which separates the center of the cyclone from the warm air. With the center of the cyclone surrounded by cool air, the temperature difference or

baroclinity In fluid dynamics, the baroclinity (often called baroclinicity) of a stratified fluid is a measure of how misaligned the gradient of pressure is from the gradient of density in a fluid. In meteorology a baroclinic flow is one in which the densi ...

begins to decline, and the jet stream persisting over the strongest areas of

which is not over the center of the cyclone, which makes it so that the

jet stream Jet streams are fast flowing, narrow, meandering thermal wind, air currents in the Atmosphere of Earth, atmospheres of some planets, including Earth. On Earth, the main jet streams are located near the altitude of the tropopause and are west ...

is unable to support the system. This usually causes

decay Decay may refer to: Science and technology * Bit decay, in computing * Software decay, in computing * Distance decay, in geography * Decay time (fall time), in electronics Biology * Decomposition of organic matter * Tooth decay (dental caries ...

and

dissipation In thermodynamics, dissipation is the result of an irreversible process that takes place in homogeneous thermodynamic systems. In a dissipative process, energy (internal, bulk flow kinetic, or system potential) transforms from an initial form to a ...

of the cyclone. When an extratropical cyclone has completed cyclolysis, it usually is not connected to any

weather fronts A weather front is a boundary separating air masses for which several characteristics differ, such as air density, wind, temperature, and humidity. Disturbed and unstable weather due to these differences often arises along the boundary. For in ...

. Extratropical cyclones in the

northern hemisphere The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's Nort ...

tend to undergo cyclolysis over the northeast

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

, northwestern

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

, the

Gulf of Alaska The Gulf of Alaska (Tlingit: ''Yéil T'ooch’'') is an arm of the Pacific Ocean defined by the curve of the southern coast of Alaska, stretching from the Alaska Peninsula and Kodiak Island in the west to the Alexander Archipelago in the east, ...

, the

Pacific Northwest The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though ...

, northeast

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

, central

Russia Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...

, or the eastern

Mediterranean sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ea ...

. In the southern hemisphere, most extratropical cyclones undergo cyclolysis north of 50°S.

Tropical cyclones

Tropical cyclones A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depend ...

often undergo cyclolysis after making

landfall Landfall is the event of a storm moving over land after being over water. More broadly, and in relation to human travel, it refers to 'the first land that is reached or seen at the end of a journey across the sea or through the air, or the fact ...

, especially if the land is mountainous as the friction with the terrain is increased. Its supply of warm, moist maritime air is also cut off when it moves over land. However, the

brown ocean effect The brown ocean effect is an observed weather phenomenon involving some tropical cyclones after landfall. Normally, hurricanes and tropical storms lose strength when they make landfall, but when the brown ocean effect is in play, tropical cyclon ...

may cause the tropical cyclone to strengthen or maintain its strength over land. A tropical cyclone may also undergo cyclolysis if it moves over water cooler than as this will cause it to lose its tropical characteristics and become a

remnant low A post-tropical cyclone is a former tropical cyclone that no longer possesses enough tropical qualities to be considered a tropical cyclone. The word may refer to a former tropical cyclone undergoing extratropical transition or a tropical cyclone ...

. However, these remnant cyclones may persist for a few more days. Excessive

wind shear Wind shear (or windshear), sometimes referred to as wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical or horizontal ...

can also cause cyclolysis as it causes the

convection Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convec ...

that powers the tropical cyclone to move away from the center.

Mesocyclones

Mesocyclones A mesocyclone is a meso-gamma Mesoscale meteorology, mesoscale (or storm scale) region of rotation (vortex), typically around in diameter, most often noticed on radar within thunderstorms. In the northern hemisphere it is usually located in the ...

are localized storms, approximately to in diameter within strong thunderstorms. Thunderstorms containing persistent mesocyclones are supercell thunderstorms. Mesocyclones typically undergo cyclolysis when the

gust front An outflow boundary, also known as a gust front, is a storm-scale or mesoscale boundary separating thunderstorm-cooled air (outflow) from the surrounding air; similar in effect to a cold front, with passage marked by a wind shift and usually a ...

of the storm blocks off the updraft. At this point, cyclonic circulation weakens, and tornadic supercells lift off the ground. The thunderstorm begins to dissipate as well.

References

{{Cyclones Atmospheric dynamics Synoptic meteorology and weather